Method and apparatus for vacuum packaging with plastic sheaths



July 11, 1961 T. A. LANCASTER METHOD AND APPARATUS FOR VACUUM PACKAGINGWITH PLASTIC SHEATHS Filed Aug. 26, 1957 2 Sheets-Sheet 1 INVENTORFMBOTAA/Wc/IsTE)? BY A 27 1 Z5 20 A TOR EY July 11, 1961 "r. A.LANCASTER 2,991,600

METHOD AND APPARATUS FOR VACUUM PACKAGING WITH PLASTIC SHEATHS FiledAug. 26, 1957 2 Sheets-Sheet 2 INVENTOR 7 3 /-7- Lfl/VCHSTEP 2,991,600METHOD AND APPARATUS FOR VACUUM PACKAGING WITH PLASTIC SHEATHS Talbot A.Lancaster, Canterbury, Conn. Filed Aug. 26, 1957, Ser. No. 680,136 6Claims. (Cl. 53-22) This invention relates to the art of vacuum sealedpackages, and more especially it relates to packaging With thin plasticsheets or films.

A principal object of the invention is to provide a novel method andapparatus for wrapping articles with plastic sheet or film material sothat the wrapper closely fits or sheathes substantially the entirecontour of the article.

Another object is to provide a method and apparatus for applying to anyshaped article a skin-tight covering or sheath of plastic sheet or filmmaterial.

Another object relates to a vacuum wrapped article of regular orirregular shape which is provided with a skintight vacuum-sealedwrapping of thermoplastic material.

Various kinds of vacuum wrappings have been devised for wrapping foodproducts or other irregularly shaped articles in plastic coverings. Thusone known method requires the preparation of the wrapper as a bag orpouch, into which the article is inserted through the open end of thepouch. If a vacuum wrapping is required, a suction tube is inserted intothe open end of the pouch prior to scaling that open end, after whichthe pouch is sealed and the exhaust tube withdrawn. In such cases it isusually necessary to make the pouch oversize with respect to the articleto be wrapped, and after the evacuation the pouch is subjected to atemperature high enough to cause the wrapping material to shrink ontothe article. Such a method is wasteful of the wrapping material and itrequires the storing of a large number of various shapes and sizes ofpouches, depending upon the shape and size of the article to be wrapped.

In an effort to reduce the wastage of wrapping material, it has beenproposed to make the wrapping pouch undersize with respect to thearticle which, however, requires stretching of the pouch and the forcingof the article therein. Reliance must then be placed upon the elasticityof the pouch material to cause it to conform to the wrapped article.However, such a method still requires the pre-formation of pouches ofdifferent sizes and shapes to suit different kinds and shapes ofarticles. Furthermore, while the known methods are, capable of beingpracticed by manual operations, it is somewhat diflicult to adapt themto continuous or automatic ma chine wrapping operations. Furthermore,while it is somewhat easy with conventional methods to wrap simple andregularly shaped fiat articles, such as meat slices and the like, it isdiificult and wasteful of wrapping material and time to wrap complexshaped articles such as fowl, irregularly shaped vegetables, and thelike.

In accordance with the present invention, the abovenoted and otherdisadvantages are overcome by devising a process wherein the wrappingenvelope is formed in situ during the wrapping operation, requiringmerely flat sheets of thermoplastic material. As a result of theinventive method there is produced a plastic wrapped package wherein theplastic wrapping material is closely molded to conform itself topractically all the contours of the article or item being packaged.Accordingly one of the features of this invention relates to a method offorming a vacuum sealed plastic wrapping for any shape of article, andone which renders it feasible to use automatic wrapping machines for thecontinuous automatic vacuum wrapping of a wide variety of oddly shapedarticles, to provide such articles with a skin-tight plastic evacuatedsealed wrap.

United States Patent() Other features and advantages not specificallyenumer- Matte Patented July 11, 1961 ice tain preferred forms of theinvention,

FIG. 1 is a perspective view of a device or apparatus according to theinvention and illustrating one step in the method of the invention;

FIG. 2 is a view similar to that of FIG. 1, illustrating another step inthe method;

FIG. 3 is a sectional view of FIG. 2, taken along the line 33 thereof,and illustrating a further step in the method;

FIG. 4 is a sectional view of FIG. 1, showing the parts in closed orclamped position, illustrating a further step in the method;

FIG. 5 is a view similar to that of FIG. 4, illustrating the finalsealing step;

FIG. 6 is a sectional view of the final vacuum sealed packaged article;

FIG. 7 is a sectional view explanatory of a modification of theinvention.

Referring to FIG. 1, a preferred form of device for practicing theinvention includes a pair of swingably attached metal frames 10, 11.Merely by way of illustra tion, the frames are shown as of rectangularshape, although any other shape can be employed. The two frames areidentical in shape and are of hollow tubular sheet metal construction.Frame 10 has attached there- -to a pair of flat metal extension plates12, 13, each of which carries a pivot pin 14, 15 for pivotal movement ofthe frame in respective blocks 16, 17. The said blocks are in slidableengagement with a pair of upright rods 18, 19 which can be anchored to asuitable base 20 (FIG. 3). Similarly, frame 11 carries a pair ofextensions 21, 22 and respective pivot pins pivoted in respective blocks23, 24, which blocks are also slidably supported on the uprights 18, 19.As shown in FIGS. 4 and 5, the frames 10 and 11 can be moved to a closedor parallel spaced position, or to the open position as shown in FIGS. 1to 3, and in the dotted line position in FIG. 5. The particular mannerof swingably mounting the frames as described, enables them to be movedto parallel closed spaced positions, while allowing the frames to bespaced apart a distance D (FIGS. 4 and 5). Merely for explanatorypurposes, it will be assumed that the article to be wrapped is anirregularly shaped meat product, such as chicken or fowl.

The opposing faces of frames 10 and 11 are provided with a series ofsmall openings 25, 26. Attached to the perforated frame faces arerespective soft gum rubber or sponge rubber rectangular gaskets 27, 28,each of which has a series of perforations 29, 30 in alignment with therespective frame perforations 25, 26. The gaskets 27, 28 may be ofapproximately one-quarter inch thickness. The rear side of each framehas an opening into which is sealed a respective flexible pipe 31, 32leading to an evacuating pump 33 whereby each of the frames can beevacuated to any desired degree. Likewise another flexible pipe 34 isconnected to a vacuum pump 35 which, if desired, may be the same pumpthat is connected to pipes 31, 32. However, the pipe 34 is not insertedbetween the frames until a subsequent stage in the method, as will bedescribed hereinbelow. Normally frames 10 and 11 are in their openposition, as shown in FIG. 1, and the pipes 31, 32 and 34 are shut offby suitable valves (not shown). When the frames are in their closedpositions, as shown in FIGS. 4 and 5, the spacing D is such as to giveproper clamping pressure on rubber gaskets 27, 28 to hold the plasticfirmly and provide an air-tight seal between the opposing faces of thefilm within the clamped area and around the vacuum tube 34.

too far.

When it is desired to wrap an article such as a chicken 36, the valvesfor pipes 31, 32 are opened, thereby subjecting the frames to internalevacuation. Thereupon two fiat sheets or films 37, 38 of the wrappingmaterial are then held adjacent the respective frames and as a result ofthe suction through the frame perforations and through the gasketperforations, those sheets are firmly held fiat against their respectiveframes by atmospheric pressure. I D v In accordance with the invention,the sheets 37, 38 are of a film-fonning thermoplastic. Typical of suchplastics are those of vinyl, Saran, Pliofilm, cellulose acetate,cellulose acetate-butyrate, polystyrene, polyethylene, and the like. H

At this stage either or both of the sheets 37, .38 may be warmed by anysuitable means to the softening temperature of the plastic asschematically represented by the blocks 50, 51 in FIG. 3. The article 36to be wrapped is then placed in the center of the lower plastic film 38,as indicated in FIG. 3. As a result of the softening of the film 38 andthe weight of the article, the said film tends to conform itself to thegeneral contour of the lower half of the article. placed at a properdistance below the lower plastic film to prevent the weight of thearticle from stretching it At this stage the suction tube 34 is insertedbetween the films 37 and 38, as indicated in FIG. 3, and thereafter theframes are brought together in spaced parallelism, as indicated in FIG.4. Preferably the frames are held together under suificient force, forexample by a suitable clamp 39, so as to prevent air leakage. While theclamp is shown as of a screw type, any other well known clamping orclosing device such as an air or hydraulic piston or a toggle clampcould be used. The valve or pipe 34 may then be opened so as to evacuatethe entire space between the clamped margins of the two sheets 37 and38.

Preferably the pipe 34 is of rigid construction so that the soft rubbergaskets 27 and 28 can conform themselves around the pipe so as tomaintain an airtight seal for the evacuation of the space between theplastic sheets. As a result of the evacuation through the pipe 34, andas a result of the positive external air pressure on the outside of thefilms 37, 38, and since these films are in a softened or plastic state,they mold themselves permanently and in a sheath-like contact around thecontours of the article 36, as indicated in FIG. 5.

After the desired amount of air has been removed from the space betweenthe sheets 37 and 38, and the skin-tight fit around the article has beeneffected, the suction tube 34 can be withdrawn and the two films can beheat sealed in the marginal area around the article. The heat sealingmay be accomplished by the use of sufiicient over-all heat to bring thethermoplastic films to their sealing temperatures. Preferably, however,a supplementaryheat-sealing device 40 of any well known construction maybe lowered into heat sealing relation with the marginal areas of thefilms 37, 38. If the sealing unit *40 is of the well known impulsesealer or bar type sealer, well known in the plastic sealing art, itshould be smaller in outside dimensions than the inside dimensions ofthe frames so as to permit it to fit inside the frame and to be broughtinto close marginal sealing position with respect to the plastic films.Alternatively, the sealer may be built into the frames by means of aheating ribbon attached to the soft rubber gasket of one plate. In thisinstance it would be preferable to use a heat resistant rubber such assilicone and the sealing may be by either impulse or heated barprinciple. It is common practice to construct heat sealers with the heatsource on one side only, and the other side consisting of a siliconerubber resilient material. After the heat sealing around the margins ofthe article has been completed, the frames and 11 are opened and thecomplete vacuum sealed package is removed. 'If desired, the ex- Asupport may be cess film around the sealed area may be trimmed away toleave a relatively narrow thin or sealed margin 41 (FIG. 6) around thesealed package.

It will be understood that the invention is not necessarily limited tothe heating of the plastic films 37, 38 prior to closing the frames 10and 1 1. For example, after the said plastic films 37, 38 have beensuctionally clamped against the opposed faces of the two frames, theframes may be moved to their closed parallel relation as shown in FIG.4, and then the plastic films may be heated to their softeningtemperature while the volume of space between the two film's, as definedby the clamped margins of those films, can be subjected to the requiredsuction. It will be understood, of course, that the said suction may beapplied either before, during or after the application of the softeningheat to the films 37 and 38. Thus the shrinkage of the film or films byheating rnay be effected after the final sealing, instead of prior tothe final sealing, as above described. 7

Furthermore, while the method above described employs a suction clampingof the films 37 and 38 against the two clamping frames 10 and 11, itwill be understood that any other well known manner of holding orclamping the said plastic films against the opposed clamping faces oftheframe members can be employed. However, by using the suction method ofclamping as above described, it is practical to insert and remove thesuction tube 34 without difiiculty, while enabling the attaining of aleak-proof seal between the resilient faces of the frames. It will beunderstood that whereas the apparatus described uses hinged frames andmechanical clamping, this machine can be constructed using any wellknown method of closing and clamping, such as air or hydrauliccylinders, cam or gear action, and the like. Furthermore, instead ofusing individual or pre-cut sheets of plastic films, the thermoplasticmay be fed to the machine from two rolls of film of the proper width andeach individual package either cut from the strip of packaged articlesor allowed to remain in a strip of two or more for multiple marketing,as desired.

It will be understood, furthermore, that the invention is not limited tothe particular materials which have been mentioned for the variousparts.

The invention can also be practiced using only one film of plasticmaterial. For example the lower film 38 may be replaced by a paper orcardboard stock which has its surface coated with a material which isheat scalable to the upper plastic fihn 37, in the same manner as abovedescribed. Thus, as shown in FIG. 7, the upper plastic film 37 has beenscaled to the surface of a cardboard plate-like support 42, the surfaceof which has been pre- -.Viously coated with a layer 43 of a materialwhich readily 'seals to the plastic film 37, as above described. Theembodiment of FIG. 7 is particularly desirable in packaging flimsy orsoft materials, such as textiles or soft meats, for example liver andthe like. In either embodimerit the final package is a vacuum sheathwrapped product which is hermetically sealed and, of course, the plastic37 and the plastic 38 may be of clear transparent article of any regularor irregular peripheral surface contour, which comprises, fastening apair of unperforated thermoplastic sheets which are free from preformedsurface distortions each against a respective upper and lower windowedframe, resting the article on the 's'heet faster'fed to are lower frame,subjecting each sheet while on its frame to an initial softening heat,closing the frames to clamp the margins of the softened sheetscompletely around the article whereby the weight of the article causesthe lower film to conform itself to the general contour of the article,evacuating the entire volume of space defined by the clamped margins andthereby to cause both of the softened sheets to collapse and completelyconform themselves against the contour of the article, then subjectingthe portions of the sheets in the region between their clamped marginsand the article to a final heating to seal said sheets immediatelyadjacent the periphery of the article.

2. The method according to claim 1 in which both of said thermoplasticsheets are fastened to their respective frames by suction through theinterior of the frames.

3. Apparatus for vacuum Wrapping and sealing an article of any regularor irregular peripheral surface contour, comprising, upper and lowernormally spaced supporting frames of open windowed construction, meansto fasten a pair of unperforated thermoplastic sheets against each ofsaid frames each sheet completely bridging the open window of itsrespective frame, the sheet on the lower frame serving -as the supportfor the article during the wrapping and sealing thereof, means tosubject each sheet while on its frame to an initial softening heat,means to clamp the frames together and with the article sandwichedbetween the opposing thermoplastic sheets whereby the weight of thearticle causes the lower sheet to gener-ally conform in its softenedcondition to the general contour of the lower half of the article, meansto evacuate the entire volume of space defined by the clamped margins ofthe sheets while in heat softened condition and thereby to cause both ofthe softened sheets to collapse and completely conform themselvesagainst the contour of the article, and means to subject the portions ofthe sheets in the region between their clamped margins and the articleto a final heating to seal the sheets immediately adjacent the peripheryof the article.

4. Apparatus according to claim 3 in which each of said frames is oftubular construction having openings in the walls thereof against whichsaid sheets are held by suction through the interior of the respectiveframes.

5. Apparatus according to claim 3 in which anannular heat sealing unitis arranged to be inserted through the open windowed portion of at leastone of said frames to effect the said final heating and sealing of saidsheets.

6. Apparatus according to claim- 5 in which the said walls of saidframes at the clamping margins are provided with resilient gaskets eachof which has openings in alignment with the said openings in the framewalls whereby the sheets can be fastened against their respective framesby suction through the frames and gaskets.

References Cited in the file of this patent UNITED STATES PATENTS1,387,805 Roberts Aug. 16, 1921 1,970,193 Riebel Aug. 14, 1934 2,155,445Pittenger et al. Apr. 25, 1939 2,621,129 Ramsbottomet a1. Dec. 9, 19522,690,593 Abercrombie Oct. 5, 1954 2,730,281 Prohask-a Jan. 10, 19562,749,686 Lorenz et a1. June 12, 1956 2,750,719 Wandelt June 19, 19562,780,043 Hensgen Feb. 5, 1957 2,861,405 Hanford Nov. 25, 1958 OTHERREFERENCES Modern Packaging, March 1957, article beginning on page 154.

